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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
07 January 2019 - 08 March 2019
Reliability:
1 (reliable without restriction)
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Qualifier:
equivalent or similar to guideline
Guideline:
EPA OPPTS 830.7550 (Partition Coefficient, n-octanol / H2O, Shake Flask Method)
Qualifier:
equivalent or similar to guideline
Guideline:
other: EU Method A.24
GLP compliance:
yes
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Specific details on test material used for the study:
Identification: 4,4'-(4-methylpentane-2,2-diyl)bis((heptyloxy)benzene)
Batch (Lot) Number: AS455433
Expiry date: 01 November 2020 (retest date) (taken from label)
Physical Description: Colourless to light yellow viscous liquid
Purity/Composition: 98.5%
Storage Conditions: At room temperature protected from light
Analytical method:
liquid chromatography
Key result
Type:
Pow
Partition coefficient:
> 16 000 000
Temp.:
20 °C
pH:
ca. 7
Key result
Type:
log Pow
Partition coefficient:
> 7.2
Temp.:
20 °C
pH:
ca. 7
Conclusions:
The HPLC method at neutral pH was applied for the determination of the partition coefficient (Pow) of 4,4'-(4-methylpentane-2,2-diyl)bis((heptyloxy)benzene).
The Pow value of the test item at neutral pH was > 1.6 x 10^7
The log Pow value of the test item at neutral pH was > 7.2.
Executive summary:

Four methods are available for the determination of the partition coefficient (Pow) of the test item. The principle of each method is described below:

Shake flask method

Test item is partitioned in a two-phase system of n-octanol and water. After phase separation, the concentration of the test item in both phases is determined by a suitable analytical method. The shake flask method can be used for test item with a log Powvalue in the range of.

HPLC method

A solution of the test item is injected onto a reversed-phase LC column. The log Powvalue is calculated from the retention time of the test item. The HPLC method covers log Powvalues in the range of 0 to at least 6.

Estimation method

The solubility of the test item in n-octanol and in water is determined. The quotient of the n‑octanol solubility and the water solubility is an estimation of the Pow. The estimation method can be applied if the shake flask method and HPLC method are not applicable.

Calculation method

The calculation method is based on the theoretical fragmentation of the molecule into suitable substructures for which reliable log Powincrements are known. The log Powis obtained by summing the fragment values and the correction terms for intramolecular interactions. Lists of fragment constants and correction terms are available.

The calculation method was used for a preliminary estimation of the Powof the test item. Calculation was performed using the Rekker calculation method (PrologP 6.0, module in Pallas 3.0, CompuDrug International, San Francisco, CA, USA). Based on the calculation it was decided to perform the HPLC method for the determination of the Powof the test item.

According to the guidelines, the determination of the Powof the test item should be performed in its non-ionized form. Therefore, the pKavalues of the test item were calculated using the Perrin calculation method (pKalc 5.0, module in Pallas 3.0, CompuDrug International). Based on the calculations, it was decided to perform the test at neutral pH.


 Solutions of reference substances and the test item were analyzed. The capacity factor (k') of each compound was calculated from its retention time. The log k’ values of the references substances were plotted against the known log Powvalues. A linear regression program was used to calculate the calibration curve. Linear regression analysis was performed using the least squares method. The coefficient of correlation (r) was calculated. The log Powvalue for the test item was calculated by substituting its mean log k’ in the calibration curve. The value of log Powobtained from duplicate measurements was within±0.1 log units.

Solutions of a reference substance and the test item were analyzed. Based on the retention times of the compounds the Powand log Powvalue of the test item was determined.

The Pow value of the test item at neutral pH was > 1.6 x 10^7

The log Pow value of the test item at neutral pH was > 7.2.

Description of key information

The HPLC method at neutral pH was applied for the determination of the partition coefficient (Pow) of 4,4'-(4-methylpentane-2,2-diyl)bis((heptyloxy)benzene).

The Pow value of the test item at neutral pH was > 1.6 x 10^7

The log Pow value of the test item at neutral pH was > 7.2.

Key value for chemical safety assessment

Log Kow (Log Pow):
7.2
at the temperature of:
20 °C

Additional information

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